1. Field of the Invention
This invention relates to lubricants useful in the working of metals, especially the hot rolling and cold rolling of metals, and also in the casting of metals, more especially aluminium. More particularly the invention is concerned with such lubricants which have improved roll anti-wear, and reduced friction properties.
2. Description of the Prior Art
U.S. Pat. No. 3,526,596 discloses a hot-metal working process using a synthetic lubricant consisting only of an ester of a polyol of 2 to 12 hydroxy groups with a C.sub.12 to C.sub.22 fatty acid, with no additives. Examples are polyethylene glycol dioleate; tritallowate of trimethylol ethane and tetraoleate of pentaerythritol.
U.S. Pat. No. 3,701,730 discloses synthetic ester base-stock lubricants for engine and gear lubrication. The lubricants essentially contain as an extreme pressure additive a dibrominated neopentyl glycol ester. They optionally also contain an alkyl, aryl or alkaryl triester of phosphoric acid. The preferred triester is tricresyl phosphate. The synthetic ester base oils of the lubricants are esters of C.sub.1 to C.sub.20 alcohols, especially C.sub.4 to C.sub.12 ; and C.sub.3 to C.sub.20 aliphatic carboxylic acids, especially C.sub.4 to C.sub.12. Preferred are polyalcohols such as pentaerythritol, dipentaerythritol and trimethylol propane; and C.sub.3 to C.sub.12 monocarboxylic acids. Lubricants with base oils very similar to the aforesaid preferred types and with additives which include aryl phosphates and various long chain alkyl phosphates are disclosed in U.K. Pat. Nos. 1,180,389; 1,162,317 and 1,256,999.
U.K. Pat. No. 1,186,180 describes lubricant additives which are phosphorous-containing di-, tri-, tetra-, and hexa-carboxylic esters and complex esters. Pentaerythritol esters of C.sub.4 to C.sub.10 monocarboxylic acids are examples of many compounds reacted by heating with esters of a phosphorus-containing acid, to form the additive product.
Finally, in U.K. Pat. No. 904,964, a metal working lubricant is suggested using an ester of a polyhydric alcohol and tall oil, together with an ester of a polyhydric alcohol and fatty acids from animal fats and/or vegetable fats or oil and/or fish oils and/or pure fatty acids, and possibly also together with an additive containing phosphorus, the single example being tricresyl phosphate.